The adsorption of hydrogen on nickel catalysts. I. The effect of sintering

Abstract

1. 1. Measurements of isobars for the adsorption of hydrogen at 0.1 mm. pressure on evaporated nickel films sintered at various temperatures show that the ratio of slowly sorbed hydrogen to rapidly adsorbed hydrogen increases with the sintering temperature of the film. 2. 2. It has been shown that the slow “activated adsorption” of hydrogen on nickel, which has been previously observed by several investigators, is not adsorption but is slow sorption of hydrogen into the interior of the metal structure. 3. 3. Sites which are occupied by hydrogen which is slowly sorbed into the interior of the metal structure are not accessible to chemisorption of carbon monoxide or van der Waals' adsorption of krypton, nor are they accessible to ethylene. 4. 4. The very fast adsorption (chemisorption) of hydrogen at liquid nitrogen temperature is a true measure of the surface available for chemisorption of CO and for van der Waals' adsorption of krypton and for surface reactions such as the hydrogenation of ethylene. 5. 5. The experiments and conclusions by Taylor and Shou-Chu Liang (6, 7) regarding “The Heterogeneity of Catalytic Surfaces for Chemisorption,” parts I and II, may deserve reexamination in the light of the present experiments because of the possibility that their observed slow adsorption is also not adsorption but sorption into the crystal structure and thus noncontributing to catalysis.